Headlight dimmer system



July 10, 1956 G. W. ONKSEN, JR., ETAL HEADLIGHT DINNER SYSTEM Filed June1, 1950 W m. p

nited States Patent HEADLIGHT DIMM'ER SYSTEM George W. Onksen, Jr., andCharles W. Miller, Anderson, Ind, assignors to General MotorsCorporation, Detroit, Mich, a corporation of Delaware Application June1, 1950, Serial No. 165,392 11 Claims. (Cl. 315-83) The presentinvention relates to light sensitive control systems and moreparticularly to such light sensitive control systems as operateheadlight control means for automotive vehicles for automaticallyswitching between high beam and low beam filaments. Conventionalautomobile headlighting systems provide both what may be termed an upperand a lower beam, the first being utilized for high speed country nightdriving where it is necessary for the operator to see some distanceahead of the car. However, this amount of light and its direction areconsiderably annoying to an approaching driver and prevent him fromadequately seeing his path ahead. In passing other vehicles, therefore,it is customary to switch the headlights to the low beam, whichconcentrates the lighting just ahead of the vehicle and prevents it fromshining into the eyes of the oncoming driver. These systems have in thepast been operated by a foot dimmer switch on the floor of the driverscompartment. However, it has been proposed to actuate means for changingfrom high beam to low beam due to approaching light rays automatically,and such a system is disclosed and illustrated in a co-pendingapplication S. N. 37,984, filed July 10, 1948, in the names of George W.Onksen and Charles W. Miller, issued as Patent No. 2,679,616 on May 25,1954. The present disclosure is an improvement over the above identifiedapplication.

In both of these disclosures the main system may be described asconsisting of an electronic system which is energized from a suitablesource of power to maintain the headlights on upper beam position fornormal open country driving. Upon the appearance of oncoming light ofsufiicient intensity, the electronic system is biased to cut off,deenergizing the electromagnetic switching means and permitting springmeans to pull additional switching means to the low beam position. Anauxiliary foot switch is also provided in either system to provide meansfor overriding the automatic and give a high beam at the will of theoperator. In the system disclosed in S. N. 37,984, a phototube was usedas the sensitive light element which was connected to a voltageamplifier tube and caused the latter to conduct when the oncoming lightintensity reached a predetermined value.

It is an object of the present invention to provide a single lightsensitive and amplifying means toprovide the controlling voltages forthe headlight dimmer system.

It is a further object of our invention to utilize a photomultipliertube to provide the controlling voltages, for a headlight dimmer system.

It is a still further object of our invention to provide a satisfactoryhigh voltage power supply for the headlight dimming system utilizing aphotomultiplier tube.

It is a still further object of our invention to provide an automaticheadlight dimming system which is substantially unaffected byinterference such as created by the ignition systems of internalcombustion engines.

It is a still further object of our invention to provide an automaticelectronic headlight dimming system that maintains stable operation overlong periods without necessitating readjustment.

2,754,452 Patented July 10, 1956 It is a still further object of ourinvention to provide an automatic electronic headlight control systemwhich uses commercially available tubes without the necessity forspecial selection.

With these and other objects in view which will become apparent as thespecification proceeds, our invention will be best understood byreference to the following specification and claims and theillustrations in the accompanying drawings, in which the figurerepresents a schematic circuit diagram of a headlight dimmer systemutilizing the embodiments of our invention.

Referring now more specifically to said diagram, there is shown thereinan incoming power line 2 connected to a multiple position switch 4 whichmay engage either one of two stationary contacts 6 or 8. Contact 8 isconnected through conductor 10 to a radio frequency choke coil 12 andthence through one section of condenser 14 to line 16, terminating inthe mid-point of a transformer primary coil 18 of transformer 20. Oneend of the primary 18 is connected through line 22 to a stationarycontact 24 of multiple contact vibrator 26. The other side of thetransformer primary 18 is connected in like manner through line 28 tospaced opposed stationary contact 30 and also to one end of the vibratoroperating coil 32. The other end of the operating coil is connecteddirectly to the vibratory reed 34, which is in turn connected throughits mounting and conductor 36 to the other side 38 of the condenser 14and to ground. A second pair of spaced stationary contacts 40 and 42 areconnected through lines 44 and 46 respectively, with the outsideterminals of the secondary coil 48 of the transformer 20. A resistor 50and condenser 52 are connected in series across the secondary 48.

The center tap of the secondary 48 is connected through line 54 to oneend of a resistor 56, which is connected in series with two additionalresistors 58 and 60 to form a voltage divider, the remote terminal ofthe latter being connected to ground through line 62. A condenser 64 isconnected between line 54 and ground. A conductive line 66 is connectedbetween resistances 58 and 56 and extends to a voltage regulator tube 68and thence through line 70 to the input circuit of a high frequencyoscillator. The oscillator system is enclosed in dash outline in thelower left hand corner of the figure and is adapted to utilize aregulated portion of the output of the multiple contact vibrator powerpack, which may be, for example, 150 volt D. C. and change this to highfrequency and of the proper high voltage. The dash outline around theoscillator indicates an aluminum shield 72 which is grounded.

The oscillator tube 74 has its plate 76 connected through line 78 with atuned resonant circuit consisting of an industance 80, a variablecapacitor 82 and a fixed capacitor 90, the opposite terminals of whichare connected to incoming line 70 and also through line 84 and resistor86 back to screen grid 88 of the tube 74. Inductance forms one part of amulti-part air core transformer group consisting of coil 80, coil 92 andcoil 94, all of which are mounted in juxtaposition, so that currentsflowing in one will induce corresponding proportional currents in theothers. Condenser 96 is connected between grid 88 and ground. Controlgrid 98 of the tube 74 is connected through line 100 to line 102, whichis in turn connected to one terminal of the coil 94. The oppositeterminal of the coil 94 is connected through line 104 and through afilter network composed of capacitor 106 and resistance 108 in parallelto ground and to the cathode 110 of the tube. A variable condenser 112is connected between line 100 and line 78. Coil 92 has one terminaldirectly connected to the anode 114 of a diode rectifier 116, thecathode 118 of which is grounded. The other terminal of the coil 92 isfiltered to ground through condenser 93 and is connected through line120 with one end of a plurality of small resistances 122, 124, 126, 128,130, 132, 134, 136, 138 and 140 in series, the number of resistancesequaling the number of stages in the photomultiplier tube 188. Thisprovides a required high D. C.

voltage supply for the photo-multiplier tube and it may of the series,is connected through line 62 to ground. The

intermediate points between each of the series of resistors justreferred to are connected through protective resistances 144, 146, 148,150, 152, 154,156, 153 and 16% to a plurality of dynodes 164i, 166, 163,17%), 172, 174, 176, 178 and 180 respectively. The first or lowestresistor 222 has its outside terminal connected in like manner throughresistor 182 to a central cathode 184.

The output electrode or plate 186 of the photo-multiplier tube 188 isconnected through line 196 with gri- 1-92 of the current amplifying tube1%, the plate 1% of which is directly connectedthrough line 198 withline 200, which ex'tendsto one terminal of control relay 262.

The opposite terminal of control relay 202 is connected through line 204to a point intermediate resistors 56 and 58. Line 1% is also connectedto one end of a resistor 206, the opposite end of which is connectedthrough line 208 to a tap between resistors 58 and 6d. The cathode 2100fthe tube 194 is directly connected to adjustable tap 207 on resistor 58to adjust the release of the circuit without affecting the dimming pointwhatsoever. An adjustable tap 212 on resistance 266 is connected throughline 214 to cathode 216 of a diode rectifier tube 213. The anode 220 ofthis last named tube is connected through line 222 to control grid 224of a current amplifier tube 226. The control grid 224 is also connectedthrough line 228 and resistor 23% to ground. The cathode 231 isconnected to ground. The plate 232 of tube 226 is connected through alimiting resistor 234 to line 2%.

Line 260 is also connected through resistor 236 to line 238 and thenceto an auxiliary overriding foot switch 240,

which provides manual override for the system. Line 242, which isconnected to some suitable source of power, is also connected to themovable armature 244 of relay 2132, which is normally spring biased byspring 246 to be spaced away from its stationary contact 248, but whichis brought into contact therewith when the relay 292 is energized.Contact 248 is connected to line 25%) which extends to a furtherstationary spaced contact 252, engageable by a movable switch arm 254,which is the standard ratchet type foot switch and oscillates betweenstationary contact 252 and stationary contact 256, and is for highlowbeam operation. Resistor 243-condenser 245 network is connected betweenlines 242 and 250 to prevent arcing between armature 244 and contact243.

Contact 256 is'connected through line 258 to stationary contact 6.Oscillatory contact 254 is connected through line 260 to relay coil 262,the opposite terminal of which is grounded. Movable armature 264 ofrelay 262 is connected to a suitable source of power and is springbiased as shown by spring 270 to engage an upper stationary contact 266which completes the circuit through line 268 to the low beam filaments.Thus, with the spring dominating, the circuit will be maintained on lowbeam. if, however, relay 262 is energized, attracting its armature 26 inopposition to spring 270, it will come down into contact with stationarycontact 272, which is connected through line 274 with the high beamfilament circuit and thus through this switching action the low beamelements are deenergized and the high beam energized.

In the operation of the device lead 2 is connected to the standardheadlighting switch and may be considered to be the main source ofpower. Selector switch 4 is a manually operated switch and determinesfrom its position whether the headlight system shall be conditioned forsocalled standard foot switch operation or shall be automaticallyelectronically controlled. When switch d is in its upper position, thesystem is conditioned for normal foot switch control and when footswitch 254 is depressed against contact 256, an obvious circuit iscompleted through relay 262 to energize the same, attract its armature,and close a system through line 274 to the high beam filaments. Sinceswitch 254, 256, 252 is the conventionai ratchet type foot switch, uponthe next operation of the button, arm 254 will be placed in contact withstationary contact 252 and away from contact 256. Its contact withstationary contact 252 has no effect, inasmuch as the electronic portionof the system is deenergized, but its movement away from contact 256deenergizes relay 2622, allowing spring 270 to pull armature 264- upinto contact with stationary contact 266 to energize the low beam. Thus,with the manual switch 4 in its upper posit. n, operation of the footswitch 254 alternately energizes high and low beam filaments.

if the operator turns switch 4 to its lower position contact withstationary contact 8, then the electronic system is energized to placethe system under automatic operation. Foot switch 254 is adjusted to bein its uppermost position and the operation is as foilows: the multiplecontact vibrator 26 in the upper left hand corner of the circuitreceives D. C. power over line it through choke it, the taps oncondenser 14, and line 16 to center of the primary coil 18. As the reed34 moves back and forth through action of its coil 32 between the twosets of stationary contacts, the primary and secondary halfcircuits ofthe transformer are alternately energized to provide D. C. power on theoutput line 54 from the multiple contact vibrator section of the system.This voltage appearing on line 54 is applied to one end of a voltagedivider or potentiometer consisting of three resistances, 56, 58 and 60in series to ground. A tap line as is provided to take off a desiredvoltage from this voltage divider, which voltage then proceeds throughvoltage regulator tube 68 and appears on line 76 which is the input lineto' a high frequency, high voltage oscillator.-

The voltage appearing on line 76 is a stable voltage since it has beenregulated by the tube 68 and may for example, of the order of volts D.C. The oscillator tube 74in the high frequency, high voltage sectionreceives this 150 volt input and generates through the normal oscillatoraction of such a system a high frequency voltage inthe coils 3t) and 94of the air core transformer. The high frequency oscillator may beadjusted through the use of two variable condensers 82 and 112, althoughin some instances one of thesecondensers may be eliminated and only oneused to provide the high frequency variation. This high frequency A. C.voltage is industively applied'to the secondary coil 2 of the air coretransformer. The output of secondary coil 92 of the transformer isrectified by a rectifier tube 116 in circuit therewith,and the rectifieris so connected that tne voltage appearing on line 120 is negative withrespect to ground rather than positive.

This negative voltage of a desired value is thus applied directly acrossa plurality of small resistors 122i4ii inclusive in series, and in thismanner applies proper potential steps to each of the dynodes of thephoto-multiplier tube 188. Line 120 is connected to the main cathode 184through protective resistor 182 and an intermediate point between eachof the other resistances is in like manner connected'through aprotective resistance to each of the dynodes 'of the tube. 'Thus, thehigh frequency, high voltage power supply provides the necessary D. C.potentials for operating the phototube 133. The protective resistors 182and 144 through inclusive are supplied in order to protect the phototubefrom becoming damaged due to the suns rays impinging thereon, and wehave found that-when so protected thesephoto-multiplier tubes may beused in daylight with no damage thereto.

Light impinging upon the photocell causes an emission from the cathodewhich induces a plurality of sequential steps of secondary emissionaround the dynodes, each step causing an amplification of the emissionuntil the anode is reached, at which time the feeble original currentshave been amplified many times to reach a very useable and sizeablevalue at the anode. The photomultiplier tube therefore performs both alight sensitive pick-up function and an amplifier function and takes theplace of two tubes and a control grid resistor of extremely high valuein the system disclosed in our earlier filed application aboveidentified. By having this action take place within one tube thedifiiculties of introducing or picking up interference on the input tothe first amplifier are avoided and permit the use of this system inproximity to internal combustion engine ignition systems.

The output from the anode is applied directly to the control grid 192 ofa current amplifier tube 194, whose flow partially controls theoperation of the main relay 202. This output current is also connectedthrough tap 21.2 on resistor 206 with the cathode in the diode 218 whichis directly connected to the control grid of a second current amplifiertube 226, having in its output a limiting resistor 234, which in turn isconnected to relay 202. In the operation of this portion of the system,when both tubes 194 and 226 conduct, relay 202 is energized to attractits armature 244 and close an obvious circuit from the power line 242through relay 262 to energize the latter and pull the headlights to highbeam. Upon a decrease in current fiow in tube 194, which is biased tocut off first through the voltage applied to cathode 210 from thevoltage divider, relay 202, being energized, will not drop out, therestill being a sufficient flow through tube 226, which is biased at amuch lower point, to maintain this relay energized. However, assumingthat the current has now decreased below this value through tube 226alone, the relay now drops out, permitting the headlights to go to lowbeam due to the action of the spring 270. If the current now begins torise, it will increase first through tube 226 until it reaches themaximum value in that tube, which will still be insufiicient to pull inrealy 202 until such time as tube 194 conducts to energize this realyand close its switch 244-248 to return the headlights to upper beam.Thus adjustment of capacitors 82 and 112 to vary the output of theoscillator will determine the dimming point when tube 226 falls to sucha value that relay 202 drops and adjustment of tap 207 on resistor 58will determine the reenergizing point of relay 202.

Let us thus assume normal country driving with the manual switch 4 setin its lower position, foot switch 254 in its upper position, and nolight falling on the photocell. With no light on the photocell,substantially no current flows through line 190 and control grid 192 of"tube 194 is approximately at the same voltage potential as cathode 210.Also for the same reason control grid 224 of tube 226 is at the samevoltage potential of its cathode. Under these conditions both tube 194and 226 conduct current and relay 202 is energized. Switch 244 248actuated thereby is closed, energizing relay 262 and closing switch264272 thus energizing the headlights on the high beam. Assume a vehicleis approaching and the impinging light from its headlights falls on thephoto-multiplier tube 188, causing it to conduct and amplify, loweringthe potentials of grids 192 and 224 to first a point at which tube 194cuts off and thereafter to a point at which tube 226 falls below therequired current passage to retain relay 202 energized. That relay thenbecomes deenergized, permitting switch 244248 to open, deenergizingrelay 262, and permitting the spring operation of 270 to switch theheadlights to low beam. They will be retained on low beam until thelight is removed from the photo-multiplier tube to a sufiicient degreeto first cause increased flow through tube 226, and latterly flowthrough tube 194, which latter will permit b relay 202 to becomeenergized and attract its armature 244, again switching to high beam. Itis to be noted in this regard that the ratio of current flow through thetwo tubes 194 and 226 may be varied by moving the adjustable resistortap 212 along resistor 206.

If, upon having the automatic system of the car switch the headlights tolow beam, the operator then desires to manually override the system,since perhaps the oncoming driver has refused to dim his lights, andgive a momentary high beam flicker, this may be accomplished by theoperator closing a second foot switch 249, which closes an obviousenergizing circuit for relay 292 and will keep that relay energized aslong as it is closed to maintain the headlights on high beam.

The multiple contact vibrator system is, of course, utilized in order toprovide a relatively high voltage from a low voltage source such, forexample, as a storage battery, and may in this instance supply asufficient voltage to line 54 to give a desired regulated D. C. voltageon line 79, which, as mentioned above, may be, in the present system, inthe order of volts. It is, of course, well-known that thephoto-multiplier tube does require a high voltage, and this is providedby the high frequency oscillator 7 4. The voltage needed by thephotomultiplier tube may vary, it has been found, from 1100 volts to 400volts, and it might be added in this regard that it is preferred in thepresent instance to use a negative voltage rather than a positive one.The desired variation between 400 and 1100 volts may be provided byadjustment of the condenser 32 or condenser 112, but once thisadjustment has been made for the actual phototube installed and for thetransformer S0-9492 used, it is not necessary to again make any furtheradjustment. While the output of the high frequency oscillator has beenshown as rectified to supply D. C. voltage, A. C. can in many instancesbe used if the losses are not too great between the oscillator andphoto-multiplier tube.

The resistances in series with each of the dynodes have een insertedtherein in order to permit the usage of the photo-multiplier tube indaylight, as it was found early that these tubes could not be usedwithout a current limiting means in series therewith in sunlight, orthey would burn out. It has been found that the present system is muchless sensitive to interference from the automobile ignition system thatit is much less sensitive to variations due to moisture, and that thestability in continued operation is very good. The pick-up and bulk ofthe amplification takes place in the photo-multiplier tube per se, andis, therefore, much less apt to be affected by outside conditions.

We claim:

1. In a system for automatically dimming multiple filament headlamps, aregulated source of power, switching means for alternately energizingdifferent filaments of the headlamps, high frequency oscillator meansconnected to the source of power to supply high voltage, photomultipliermeans having input and output circuits, said input circuit beingconnected to the high voltage supply, current amplifier means connectedto the output of the photo-multiplier means and to the switching meansto control the energization of the filaments in response to theradiation falling on the photo-multiplier means.

2. In a system for automatically dimming multiple filament headlamps, aregulated source of power, switching means for alternately energizingdilferent filaments of the headlamps, high frequency oscillator meansconnected to the source of power to supply high voltage, voltage dividermeans connected to the output of the high frequency generator, aphoto-multiplier tube having a plurality of electrodes, :1 portion ofwhich are connected to the voltage divider, an output circuit connectedto another electrode and to the switching means to control the same asthe output of the photo-multiplier tube changes due to variations inradiation falling thereon.

3. In a power supply system, a fluctuating source of low voltage-D. C.,amplifying means connected thereto to change-the'low voltage-D. C. to ahigher voltage D. (3., voltage regulating means connected to the higherD. C. voltage, adjustable high frequency oscillator means connected tothe regulated D. C. voltage to generate a still higher A; C. voltage andrectifier means connected to the output of the oscillator to reconvertthe A. C. to an adjustable, stable D. C.

4. In a photosensitive control system, a source of regulated voltage, anadjustable high frequency oscillator connected'thereto, rectifier meansconnected to the output of the oscillator to convert it to D. C., avoltage divider connected to the rectified output, a photo-multipliertube connected to the voltage divider and supplied with power foractuation, electron amplifier means connected to the output of thephoto-multiplier tube, relay means connected to and controlled by theoutput of the electron amplifier means, the adjustment of the oscillatorvarying the power supply for the photo-multiplier tube, therefore theamount of light required to operate the relay.

5. In a photosensitive control system, a source of regulated voltage, ahi h frequency oscillator connected thereto, rectifier means connectedto the output of the oscillator to convert it to D. C., a voltagedivider connected to the rectified output, a photo-multiplier tubehaving a plurality of electrodes therein, circuit means connecting aportion of the electrodes with the voltage divider and impedance meansin series with each circuit to each electrode;

6. In a photosensitive control system for automatically dimming multiplefilament headlamps, a source of regulated voltage, a high frequencyoscillator connected thereto, rectifier means connected to the output ofthe oscillator to convert it to D. C., a voltage divider connected tothe rectified output, a photo-multiplier tube having a plurality ofelectrodes therein, circuit means connecting a portion of the electrodeswith the voltage divider, impedance means in series with each circuit toeach electrode, an output circuit connected to a further electrode,current amplifier means connected to said output and switching meansconnected to the current amplifier means and to the multiple filamentsto control the same.

7. In a photosensitive control system for automatically dimming multiplefilament headlamps, a source of low voltage, D. C. multiple contactvibrator means connected thereto for amplifying the same to a higher D.C. voltage, a high frequency oscillator connected to said higher D. C.voltage as a supply, rectifier means connected to said oscillatoroutput, a voltage divider connected to said rectifier means having ahigh D. C. voltage thereacross, a photo-multiplier tube having aplurality of electrodes, conductive means connecting a portion of theelectrodes to the voltage divider including an impedance in series witheach connected electrode, an output circuit connected to another of theelectrodes of the photo-multiplier tube and switching means connected tosaid output circuit and to the multiple filaments to cause selectiveenergization of the filaments depending on the output of thephoto-multiplier tube as determined by radiation falling thereon.

8. In a system for automatically dimming multiple filament headlamps, asource of power, switching means for alternately energizing difierentfilaments of the headlamps, light sensitive means connected to thesource, amplifier means connected to the light sensitive means includinga pair of electronic tubes in parallel of different outputs and biasedto conduct at different voltages, relay means connected to-the amplifieroutput and operating said switching means and independent means foradjusting'the bias on one of the tubes only to determine thereenergizing point for the relay means.

9. in a system for automatically dimming multiple filament headlamps, asource of power, switching means for alternately energizing differentfilaments of the headlamps, light sensitive means connected to thesource, amplifier means connected to said light sensitive means, relaymeans connected to the amplifier output and operating said switchingmeans, said amplifier means including a pair of electronic tubes inparallel relation whose combined conductivity operates the relay means,said tubes being biased to conduct at different input voltages, alimiting resistor in series with one of. the tubes to reduce its outputso that relay energization and deenergization will take place atdifierent levels of intensity of light and means for adjusting the biason the tube not having resistance in series therewith to vary the pointof relay reenergization.

10. In a photosensitive control system for automatically dimmingmultiple filament headlamps, a source of D. C. power, switching meansfor alternately energizing different filaments of the headlamps, anadjustable high frequency oscillator connected to said source, lightsensitive means connected to the oscillator output, amplifier meansconnected to the light sensitive means including a pair of electronictubes in parallel of different outputs and biased to conduct atdifferent voltages, relay means connected to the amplifier output andoperating said switching means of the headlamps, and independent meansconnected to the source of power and one of the tubes to adjust the biason that tube so that the point of reenergization of the relay can beadjusted thereby and the point of deenergization by adjustment of theoscillator.

11. In a system for switching between a plurality of lamp filaments, asource of electrical power, switching means for selectively energizingdifferent lamp filaments, an oscillator connected to the source of powerto supply high voltage, photo-multiplier means having input and outputcircuits, said input circuit being connected to the oscillator for highvoltage supply, and amplifier means connected to the'output circuit ofthe photo-multiplier means and to the switching means to control theenergization of the filaments in response to the amount of lightradiation falling on the photo-multiplier means.

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